Published online by Cambridge University Press: 05 November 2013
2.1 Somewhat historical: overview of the Local Group, dwarf galaxies, and their observed structures
Before taking on a discussion of the dynamics of Local Group (LG) galaxies and the contributing and competing effects of dark matter and tides, it is useful to have an understanding of the spatial distribution of these galaxies, the distribution of their types and masses, and their morphologies – all of which play critical roles in defining how dark matter and tides play out their dynamical tug-of-war. The most common types of galaxies – the dwarfs – which are the most dark matter dominated as well as those among LG galaxies to show the greatest evidence for tidal effects, are the primary focus of this chapter.
2.1.1 The Local Group in context
Large-scale galaxy redshift surveys over the past decades (e.g., Davis et al., 1982; Geller and Huchra, 1989; Shectman et al., 1996; York et al., 2000; Colless et al., 2001; Strauss et al., 2002; Abazajian et al., 2009; Jones et al., 2009) have revealed clearly the filamentary structure of the distribution of galaxies in the Universe. The nearest 100 Mpc shows vast voids but several large mass concentrations, such as the Perseus-Pisces, Pegasus, Pavo, Coma, Hydra-Centaurus, and Virgo Superclusters. The Milky Way (MW) and the LG of galaxies live on the outskirts of the Virgo Supercluster, whose center lies about 15 Mpc away.
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